<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>盒子模型练习</title>
</head>
<style>
    div {
        width: 200px;
        height: 200px;
        border-top: 1px solid red;
        border-bottom: 1px solid blue;
        border-right: 1px solid blue;
        border-left: 1px solid blue;
    }

</style>
<body>
    <div></div>
</body>
</html>